FULL PRODUCT VERSION :
1.8.0_05

ADDITIONAL OS VERSION INFORMATION :
Windows 7 x64 ver 6.1

A DESCRIPTION OF THE PROBLEM :
After WindowEvent.WINDOW_ICONIFIED occurs in the owner of JWindow that set the background color to transparent, JWindow is not drawn when the WindowEvent.WINDOW_DEICONIFIED happened to owner.

ADDITIONAL REGRESSION INFORMATION:
1.7 probably all


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------


import java.awt.*;
import java.awt.event.*;

import javax.swing.*;
import javax.swing.border.LineBorder;


public class DeIconified_Bug extends JFrame {

    //
    // Static implementation.
    //
    static void ToCenterByWindow(Window frame, Window owner)
    {
        Dimension d;
        Point p = null;
        if(owner == null) {
            d = Toolkit.getDefaultToolkit().getScreenSize();
        }
        else {
            d = owner.getSize();
            p = owner.getLocation();
        }

        Dimension frameSize = frame.getSize();
        if (frameSize.height > d.height)
            frameSize.height = d.height;
        if (frameSize.width > d.width)
            frameSize.width = d.width;

        if(p != null) {
            p.x += (d.width - frameSize.width) / 2;
            p.y += (d.height - frameSize.height) / 2;
        }
        else {
            p = new Point((d.width - frameSize.width) / 2, (d.height - frameSize.height) / 2);
        }
        frame.setLocation(p);
    }

    static void createAndShowGUI() {
        DeIconified_Bug bug = new DeIconified_Bug();
        ToCenterByWindow(bug, null);
        bug.setVisible(true);
    }
    /**<pre>
     * </pre>
     *
     * @param args
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(
            new Runnable() {
                @Override public void run() {
                    createAndShowGUI();
                }
            }
        );
    }
    
    //
    // instance implementation.
    //
    DeIconified_Bug() {
        initialize();
        super.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
    }
    private void initialize()
    {
        JPanel panel = new JPanel();
        getContentPane().add(panel, BorderLayout.NORTH);
        JButton openJWindow = new JButton("Open window");
        panel.add(openJWindow);
        openJWindow.addActionListener(new OpenJWindowAction());
        openJWindow.setName("openJWindow");
        
        JPanel panel_1 = new JPanel();
        panel_1.setPreferredSize(new Dimension(300, 200));
        panel_1.setBorder(new LineBorder(new Color(0, 0, 0), 2));
        getContentPane().add(panel_1, BorderLayout.CENTER);
        super.pack();
    }
    class OpenJWindowAction implements ActionListener {
        @Override
        public void actionPerformed(ActionEvent e) {
            JLabel lbl = new JLabel("Dummy window", SwingConstants.CENTER);
            lbl.setFont( Font.decode("Monospaced bold 16") );
            lbl.setPreferredSize( new Dimension(200, 100) );
            lbl.setBackground( Color.orange );
            lbl.setOpaque(true);
            lbl.setBorder(new LineBorder(new Color(255, 0, 0), 1));

            JWindow jw = new JWindow(DeIconified_Bug.this);
            jw.getContentPane().add(lbl);
            jw.setBackground( new Color(0, true) );
            jw.pack();
            ToCenterByWindow(jw, DeIconified_Bug.this);
            jw.setVisible(true);
        }
    }
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
    // will override the processWindowEvent of owner window.
    @Override
    protected void processWindowEvent(WindowEvent e)
    {
        super.processWindowEvent(e);
        switch (e.getID()) {
            case WindowEvent.WINDOW_DEICONIFIED: {
                for (Window window: Window.getWindows()) {
                    if (window != this && window instanceof JWindow) {
                        Color c = window.getBackground();
                        if (c.getAlpha() < 0xFF) {
                            window.setBackground( new Color(c.getRGB()) ); /* no alpha */
                            window.setBackground(c);
                        }
                    }
                }
                break;
            }
        }
    }